segall



Nov. 11, 1958 SEGALL 2,860,272

' SPARKING DEVICE Filed Sept. 29, 1955 INVENTOR.

LOUIS H. SEGALL United States Patent SPARKING DEVICE Louis H. Segall, Sidney, N. Y., assignor to Bendix Aviation Corporation, Sidney, N. Y., a corporation of Delaware Application September 29, 1955, Serial No. 537,503

13 Claims. (Cl. 313---130) This invention relates to electrical apparatus and more particularly to electrode assemblies adapted for use in electrical circuits to produce electrical spark discharges.

One of the objects of the present invention is to provide a novel electrode assembly adapted for use in spark or igniter plugs in ignition systems for combustion engines and other apparatus wherein gaseous or other combustible charges require ignition.

Another object of the invention is to provide a novelly constructed type of spark gap which will, under corresponding circumstances and conditions, produce electrical spark discharges having greater energy than those producible by similar devices heretofore known.

A further object is to provide a novel shunted surface gap of the constrained or constricted type which will have a greater operating life than any comparable devices heretofore known.

Still another object is to provide a spark discharge device of novel construction whereby a high energy spark discharge may be initiated from a source of electrical energy, such as a charged condenser or the like, the voltage of which is lower than the normal breakdown or spark-overvoltage of a conventional gap having similar dimensions.

The above and further objects and novel features of the present invention will more fully appear from the following detail description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not intended as a definition of the limits of the invention.

In the drawings, wherein like reference characters refer to like parts throughout the several views,

Fig. 1 is an enlarged sectional side elevation view showing one form of device embodying the present invention, the section being taken on line 1-1 of Fig. 2;

Fig. 2 is a bottom view, partly in section, of the device of Fig. 1, the section being taken on line 2-2;

Fig. 3 is a view like Fig. l of another form of. device embodying the invention; and,

Fig. 4 is a bottom view of the device of Fig. 3.

The two embodiments of the invention illustrated in the drawings, by way of example, are of a type adapted for use as electrode or tip assemblies for spark or igniter plugs employed in ignition systems for so-called jet and gas turbine type engines. The views shown are about three to four times larger than structures in actual use on present day engines. It will be understood, however, that the invention is not limited to this specific use. The same may, for example, be incorporated in ignition devices for oil burners, reciprocating engines and the like, as well as in devices for many other uses where electrical sparks or arcs are required. Either embodiment may be used as the electrode or gap assembly in an igniter plug of the type shown in the pending application of Tullio Tognola, Serial No. 221,435, now Patent No. 2,786,158 filed April 17, 1951.

In the specific form illustrated in Figs. 1 and 2, a tubuice lar shell 10 has an internal flange 11 at one end which forms an annular ground electrode having an axial or cylindrical surface 12. If desired the electrode 11, 12 or the active margin thereof may be made of a different metal from shell 10 and suitably secured in or to the shell, such as by brazing, silver soldering or the like. A center electrode in the form of a metallic ring 14 is insulated from shell 10 and held in spaced, spark gap relation to ground electrode 11 by an insulating sleeve 15. The latter has a sliding fit in shell 10 and rests on shell flange 11. An internal flange in sleeve 15 which spaces, electrodes 11 and 14 has its inner peripheral surface 16 flush with electrode surface 12 and forms a bridge between the electrodes. This bridging surface is preferably made semi-conductive or highly resistant to the conduction of electrical energy in any known manner, such as by coating the same with carbon, graphite, finely divided metallic particles or the like. if a sufliciently high voltage is available, it is not necessary that the bridging surface be semi-conductive.

It is known that when a voltage is applied across electrodes bridged by a high resistance or a semi-conductive surface in the manner above described, especially a voltage applied by a charged condenser, a high energy spark or are may be created at a relatively low voltage, considering the width of the gap. It is a purpose of this invention to so improve a device of this character that under corresponding conditions, a more efficient spark or are possessing greater energy will be created. The improvement is based upon the provision of greater resistances to the sparking or arcing, which in turn requires the dissipation of greater energy in the spark or are.

In the form shown, this result is accomplished by mounting an insulator 17 so as to greatly restrict or constrict the air space in which the spark may occur be.- tween the electrodes or adjacent the bridging surface 16. Member 17 has an upper flanged portion which has a sliding fit in sleeve 15 and rests on the upper surface of ring electrode. 14. A cylindrical portion of member 17 has a close fit in ring 14 and forms a highly constricted annular gap or passage 18 with the electrode bridging surface 16. The lower end of member 17 preferably is, but need not necessarily be, flush with the lower surface of sleeve 15. The radial width of gap or passage 18 may be either uniform or tapered and the surface of member 17 forming the inner surface of the passage may be highly resistant or semi-conductive, the same as bridging surface 16.

Superposed on member 17 is a tubular insulator 19, an enlarged portion of which has .a sliding fit in sleeve 15. The parts of the assembly are held in assembled relation by a ring 20 which engages an external shoulder on member 19 and is either press-fitted, brazed or screwed into shell 10. If desired, a tubular shell member 22, the end. of which spans the ends of shell 10 and ring 20, may be heliar-c welded toshell 10 to further secure the assembly. Matching radial slots are provided in the adjacent ends of members 17 and 19 for the passage of a conductor 21 for use in connecting ring electrode 14 to a source of electrical energy.

The modification shown in Figs. 3 and 4 comprises a tubular shell 30 having a ground electrode 31. An insulating sleeve 32 has a sliding fit in the shell and rests on electrode flange 31. An internal surface 33 of sleeve 32 is flush with the inner axial surface of annular electrode 31 .and is preferably semi-conductive. A reduced portion of the bore through sleeve 32 is threaded for receiving a center electrode 34. The latter has an external end flange which fits into the bore of sleeve 32 and engages an internal shoulder therein. The lower end of center electrode 34 is centrally countersunk to receive a reduced portion of an insulator 35, the en- 3 Iarged portion of which fits within surface 33 to form a constricted annular passage 36. The sole communication between electrodes 31 and 34 is accordingly through passage 36 along the semi-conductive surface 33. If desired, the external surface of the enlarged part of member 35 may also be semi-conductive.

Insulator 35 and center electrode 34 may be held in assembled relation in any suitable manner, such as by a rivet 37. Center electrode 34 may be connected to a source of electrical energy in any of many suitable ways known to the art. Sleeve 32 and hence, the center electrode assembly is held in shell 30 by a ring 38 which may in turn be further secured by tube 39 which is welded to shell 30.

In some successful embodiments of the invention the constricted annular passaegs 18 and 36 have had radial widths on the order of .003 to .008 inch. This width can of course be increased somewhat and still produce an improvement over known constructions. Accordingly, the term constricted gap or passage as herein used will be understood to mean a gap having a width of the order of .050 inch or less.

There is thus provided a novel spark gap device which is capable of efficiently converting electrical energy into an electrical are or spark whereby a substantial percentage of the available energy is converted to heat for use in igniting a combustible medium. The novel structure is also capable ofgenerating a hot spark which is inherently projected into a combustible medium in a pattern which initiates combustion more efficiently and with greater assurance than is possible with prior known devices for the same purpose. This device is also of simple construction and may be manufactured in quantities with facility and at low cost.

Although only a limited number of embodiments or modifications of the invention have been illustrated in the accompanying drawings and described in the foregoing specification, it is to be expressly understood that the invention is not limited thereto. For example, the walls of the constricted annular passages in Which the spark is generated may diverge slightly from each other or one from the other. -If desired, the central insulating means 17 or 35 may be somewhat shorter or extended int-o and even through the center of the ground electrode. Various other changes may also be made, particularly in the detailed construction and arrangement of the parts illustrated, without departing from the spirit and scope of the invention as the same will now be understood by those skilled in the art.

What is claimed is:

1. A spark gap device comprising a tubular insulator, annular electrode means engaging one end of said insulator and having an internal diameter substantially equal to the diameter of the adjacent portion of the bore of said insulator, a center electrode in the bore of said insulator in spark gap relation to said annular electrode, and insulating means within said insulator and forming therewith a narrow annular passage through which any electrical flash-over between said electrodes must occur.

2. A spark gap device as defined in claim 1 wherein said center electrode is supported in said insulator and said insulating means is supported by said center electrode.

3. A spark gap device as defined in claim 1 wherein said center electrode is annular and disposed between annular flanges on said insulator and said insulating means.

4. A spark gap device comprising an insulator having a passage therethrough, an annular electrode engaging said insulator and having an inner periphery the diameter of which is substantially the same as the diameter of the adjacent portion of the passage in the insulator, an electrode in said passage terminating in spark gap relation to said annular electrode, and insulating means centrally disposed in said insulator and forming a narrow annular passage with that portion of the internal wall of said insulator which bridges the gap between said electrodes.

5. A spark gap device as defined in claim 4 wherein the radial width of said annular passage is within the range of .003 inch to .050 inch.

6. A spark gap device as defined in claim 4 wherein the surface of said bridging wall is semi-conductive.

7. A spark gap device comprising two insulators arranged to form a radially narrow annular passage, and an electrode at each end of said passage in spark gap relation with each other through said passage, at least one end of said passage being open.

8. A spark gap device as defined in claim 7 wherein one end of said passage is covered by one of said electrodes.

9. A spark gap device as defined in claim 8 wherein the other of said electrodes is annular and has an inner periphery of substantially the same diameter as the outer diameter of said annular passage.

10. A spark gap device as defined in claim 7 wherein the radial width of said annular passage is within the range of .003 inch to .050 inch.

11. A spark gap device as defined in claim 7 wherein the surface portion of said annular passage which bridges the gap between said electrodes is semi-conductive.

12. A spark gap device as defined in claim 7 wherein both electrodes are annular.

13. A spark gap device as defined in claim 12 wherein one of said electrodes bridges one end of said annular passage and the other of said electrodes has an axial surface constituting an extension of the surface of one of the walls of said annular passage.

References Cited in the file of this patent UNITED STATES PATENTS 

